JP2002232046A - Optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize bidirectional and broadband optical amplification with the small number of devices. SOLUTION: An optical circulator 40 feeds signal lights Ca and La from a terminal station 10 to an EDF 44 for C-band amplification, and an optical circulator 42 feeds signal lights Cb and Lb from a terminal station 16 to an EDF 48 for C-band amplification. An EDF 46 for L-band amplification is arranged between the EDFs 44 and 48. The excited lights outputted from laser diodes 50 and 54 are respectively introduced into the EDFs 44 and 48 by WDM optical couplers 52 and 56. Exited lights not absorbed in the EDFs 44 and 48 are inputted into the EDF 46 to excite the EDF 46. Band separation filters 58 and 60 respectively separate the lights Ca and Cb amplified in the EDFs 44 and 48. An optical coupler 62 synthesizes the amplified light La from a C port of the circulator 42 with the amplified light Ca from the filter 58, and an optical coupler 64 synthesized the amplified light Lb from a C port of the circulator 40 with the amplified light Cb from the filter 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband optical amplifier, and more particularly, to a wideband optical amplifier capable of optically amplifying C and L bands.

[0002]

2. Description of the Related Art With the recent demand for data communication, 1530
In addition to the existing wavelength band of １５1560 nm (so-called C band), the use of longer wavelengths of 1570 to 1610 nm (so-called L band) is being studied. C
A broadband optical amplifier capable of optically amplifying both the band and the L band is described in, for example, US Pat. No. 6,049,417.

Further, an optical amplifying device in which an optical amplifying medium amplifies signal light bidirectionally has been studied as an optical amplifying device for a bidirectional optical transmission system for transmitting signal light bidirectionally through one optical transmission line. ing. For example, US Pat. No. 5,548,438, US Pat. No. 5,812,306, US Pat.
No. 15308, US Pat. No. 5,926,590,
US Patent No. 6,018,404 and US Patent No. 609
See No. 1542. Basically, a configuration in which two signal lights having different propagation directions are input to a single optical amplifier in the same direction by one or a plurality of optical circulators (US Pat. No. 5,548,438, US Pat. No. 5,812,306, US Pat. No. 5,926,590 and US Pat.
018404) and an optical amplifier that does not depend on the propagation direction and an optical circuit that regulates the propagation direction according to the wavelength (US Pat. No. 5,815,308 and US Pat. No. 6,091,542).

[0004]

Even in an optical transmission system in which only one-way signal light passes through one optical transmission line, a bidirectional optical amplifier leads to simplification of a repeater. However, there is no high-performance bidirectional optical amplifier that realizes a wide band while using an optical amplifying medium that amplifies signal light bidirectionally.

In a method of individually broadening the optical amplifiers for each propagation direction in a bidirectional optical amplifier having an optical amplifier for each propagation direction, the number of constituent elements increases and the reliability decreases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical amplifier having a simple structure in a wide band for independently amplifying two input lights.

[0007]

An optical amplifier according to the present invention comprises a first signal light (La) in a first band (L) and a second signal light (Ca) in a second band (C). 1) consisting of
, And the third signal light (Lb) of the first band (L) and the fourth signal light (C) of the second band (C).
b) a bi-directional optical amplifying device for amplifying each of the second input lights, comprising: a first optical amplifying medium (46) capable of amplifying the light of the first band (L); The second and third optical amplifying media (4) are disposed on both sides of the optical amplifying medium (46) and are capable of amplifying the light of the second band (C).
4,48), an excitation light source for generating excitation light for exciting the first, second and third optical amplification media, and first, second and third ports, and the first port (A ) Is supplied from the second port (B) to the second optical amplifying medium (44), and the first input light is input from the second optical amplifying medium (44) to the second port (B). A first optical circulator (40) for outputting light input to B) from the third port (C), and first, second, and third ports, and input to the first port (A). The second input light is transmitted from the second port (B) to the third optical amplification medium (48).
To the second optical amplifying medium (48).
A second optical circulator (42) for outputting light input to the port (B) from the third port (C);
Optical amplification medium (46) and the second optical amplification medium (44)
And a first wavelength separator (58) for separating the second signal light (Ca) amplified by the second optical amplifying medium (44), and the third optical amplifying medium (48) and a second wavelength disposed between the first optical amplification medium (46) and separating the four signal lights (Cb) amplified by the third optical amplification medium (48). A first multiplexing device that multiplexes the light output from the third port of the second optical circulator (42) with the light split by the first wavelength splitter (58). (62) and a second multiplexer for multiplexing the light separated by the second wavelength separator (60) with the light output from the third port of the first optical circulator (40). (64).

With this configuration, the first optical amplification medium is used for both the amplification of the first signal light (La) and the amplification of the second signal light (Lb), so that the number of optical amplification media can be reduced. Further, the signal light of the first band and the signal light of the second band can be efficiently amplified. This makes it possible to realize a wideband bidirectional optical amplifier with a simple configuration.

Preferably, further, the first multiplexer (6)
2) A first gain equalizer (6) for equalizing the gain of the output light
6), and a second gain equalizer (68) for equalizing the gain of the output light of the second multiplexer (64). Thus, the gains of the first input light and the second input light can be equalized and output.

[0010] Preferably, further, a first gain equalizer (66) for equalizing the gain of the output light from the third port of the second optical circulator (42), and the first wavelength separator A second gain equalizer (66) for equalizing the gain of the light separated in (58), and the first optical circulator (4).
0) a third gain equalizer (68) for equalizing the gain of the output light from the third port, and the second wavelength separator (60)
Gain equalizer (6) for equalizing the gain of the light separated by
8). This equalizes the gains of the first signal light and the second signal light of the first input light, and the second signal light of the first signal light of the second input light. , Can output.

Preferably, the pumping light source is a first pumping light output device (50) and a second pumping light output device (54).
And a second optical amplification medium disposed between the second port (B) of the first optical circulator (40) and the second optical amplifying medium (44), and output from the first pumping light output device (50). A first supplying an excitation light to the second optical amplifying medium (44);
WDM optical coupler (52) and the second pump light output device disposed between the second port (B) of the second optical circulator (42) and the third optical amplification medium (48). A second WDM optical coupler (56) for supplying the pump light output from the (54) to the third optical amplification medium (48);
Consists of Thereby, the first, second, and third optical amplification media can be efficiently excited.

[0012] Preferably, the pumping light source includes a pumping light output device (50, 54) for outputting the pumping light, and the first light source.
Is disposed between the second port (B) of the optical circulator (40) and the second optical amplifying medium (44), and a part of the pump light output from the pump light output device (50, 54). The first WDM to be supplied to the second optical amplifying medium (44)
An optical coupler (52), disposed between the second port (B) of the second optical circulator (42) and the third optical amplification medium (48), and connected to the pumping light output device (50,
The second WDM optical coupler (5) that supplies the rest of the pump light output from the third optical amplification medium (48) to the third optical amplification medium (48).
6). Thereby, the first, second, and third optical amplification media can be efficiently excited. The reliability of the excitation light source is improved.

For example, the first band is an L band, and the second band is a C band.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of the present invention. The transmission port Tx of the terminal station 10 is connected to the input port 32 of the bidirectional optical amplifier 30 via the optical fiber 12, and the output port 34 of the bidirectional optical amplifier 30 is connected to the reception port of the terminal station 10 via the optical fiber 14. Connect to Rx. Similarly, the transmission port Tx of the terminal station 16 is connected to the optical fiber 1
8, the input port 36 of the bidirectional optical amplifier 30 is connected, and the output port 38 of the bidirectional optical amplifier 30 is connected to the reception port Rx of the terminal 16 via the optical fiber 20.
Although the optical fibers 12, 14, 18, and 20 may be optical repeater optical fiber transmission lines including optical amplifiers, they are illustrated here as only optical fibers for easy understanding.

The terminal station 10 outputs the C-band signal light Ca and the L-band signal light La from the transmission port Tx to the optical fiber 12, and the terminal station 16 outputs the C-band signal light Cb from the transmission port Tx. And the L-band signal light Lb is output to the optical fiber 18.

The signal light Ca, La output from the transmission port Tx of the terminal station 10 propagates through the optical fiber 12 and is input from the input port 32 to the port A of the optical circulator 40 of the optical amplifier 30. Similarly, the transmission port Tx of the terminal station 16
The signal lights Cb and Lb output from the optical fiber 30 propagate through the optical fiber 18 and enter the port A of the optical circulator 42 of the optical amplifier 30 from the input port 36. Optical circulator 4
Optical elements 0 and 42 output the input light of port A from port B and output the input light of port B from port C.

Between the ports B of the optical circulators 40 and 42, three erbium-doped optical fibers (EDF) 4
4, 46 and 48 are serially connected. EDF44,4
The length of 8 and the added amount of erbium are set to amounts suitable for the amplification of the C band, and the length of the EDF 46 and the added amount of erbium are set to amounts suitable for the amplification of the L band.

The laser diode 50 generates a laser beam of 0.98 μm or 1.48 μm. Output light (excitation light) of the laser diode 50 is introduced into the EDF 44 by the WDM optical coupler 52, and excites erbium in the EDF 44. Thus, the EDF 44 functions as a C-band amplifier. Similarly, the laser diode 54
A laser beam of 0.98 μm or 1.48 μm is generated.
The output light (excitation light) of the laser diode 54 is introduced into the EDF 48 by the WDM optical coupler 56, and the EDF 48
To excite erbium in the interior. Thereby, the EDF 48 functions as a C-band amplifier. Excitation light not absorbed by the EDFs 44 and 48 and part of the C-band ASE light generated by the EDFs 44 and 48 are input to the EDF 46,
Excites erbium in DF46. With this, EDF
46 functions as an L-band amplifier.

The output lights of the laser diodes 50 and 54 may be multiplexed once and then split into two, and supplied to the WDM optical couplers 52 and 56, respectively. Such a configuration of the excitation light source increases reliability.

An EDF is provided between the EDF 44 and the EDF 46.
A band splitting filter 58 for separating the C-band light Ca amplified by 44 is arranged, and a band splitting filter 60 for separating the C-band light Cb amplified by the EDF 48 is arranged between the EDF 44 and the EDF 46. Optical coupler 6
2 multiplexes the light from the band division filter 58 with the output light from the C port of the optical circulator 42,
Combines the light from the band division filter 60 with the output light from the C port of the optical circulator 40. Gain equalizer 66
Equalizes the gain of the multiplexed output light of the optical coupler 62 and outputs the same to the output port 38. The gain equalizer 68 equalizes the gain of the multiplexed output light of the optical coupler 64 and outputs the same to the output port 34. Output.

The operation of this embodiment and the flow of signal light will be described in detail.

The terminal station 10 outputs the C-band signal light Ca and the L-band signal light La to the optical fiber 12 from the transmission port Tx. The signal light Ca, La output from the transmission port Tx of the terminal station 10 propagates through the optical fiber 12,
From the input port 32 to the optical circulator 4 of the optical amplifier 30
0 is input to port A. The optical circulator 40 receives the input light (signal light Ca, La) of the port A from the port B through the ED.
Output to F44. The output laser light of the laser diode 50 is converted by the WDM optical coupler 52 into signal light Ca, La.
Is input to the EDF 44 in the same propagation direction as that described above, and erbium of the EDF 44 is excited. The EDF 44 amplifies mainly the C-band signal light Ca among the signal lights Ca and La from the port B of the optical circulator 40, and outputs the L-band signal light La almost as it is.

The signal light Ca, L output from the EDF 44
“a” is separated into signal light Ca and signal light La by the band division filter 58, and the signal light Ca enters the gain equalizer 66 via the optical coupler 62. The signal light La is EDF4
6 is incident. The EDF 46 generates C-band ASE light by the excitation light not absorbed by the EDFs 44 and 48,
This and a part of the C-band ASE light from the EDFs 44 and 48 amplify the L-band signal light La. The L-band signal light La optically amplified by the EDF 46 is slightly amplified by the EDF 48 and enters the port B of the optical circulator 42. Since the optical circulator 42 outputs the input light of the port B from the port C, the L-band signal light La amplified by the EDF 48 eventually enters the gain equalizer 66 via the optical circulator 42.

Thus, the gain equalizer 66 has E
The C-band signal light Ca optically amplified by the DF 44 and the EDF
The L-band signal light La optically amplified at 46 is input. The gain equalizer 66 adjusts the gain of the input signal lights Ca and La, and outputs the adjusted signal lights Ca and La to the output port 38.

The signal light Ca, La thus optically amplified by the optical amplifier 30 is supplied from the output port 38 to the optical fiber 20.
And propagates through the optical fiber 20 and enters the reception port Rx of the terminal station 16.

The terminal station 16 outputs the C-band signal light Cb and the L-band signal light Lb to the optical fiber 18 from the transmission port Tx. The signal lights Cb and Lb output from the transmission port Tx of the terminal station 16 propagate through the optical fiber 18,
The optical circulator 4 of the optical amplifier 30 from the input port 36
Input to port A of port 2. The optical circulator 42 inputs the input light (signal light Cb, Lb) of the port A from the port B to the ED.
Output to F48. The output laser light of the laser diode 54 is converted by the WDM optical coupler 56 into signal lights Cb and Lb.
Is input to the EDF 48 in the same propagation direction as that described above, and erbium of the EDF 48 is excited. The EDF 48 amplifies mainly the C-band signal light Cb among the signal lights Cb and Lb from the port B of the optical circulator 42, and outputs the L-band signal light Lb almost as it is.

The signal light Cb, L output from the EDF 48
b is separated into signal light Cb and signal light Lb by the band division filter 60, and the signal light Cb enters the gain equalizer 68 via the optical coupler 64. The signal light Lb is EDF4
6 is incident. The EDF 46 is, as described above, the EDF 4
C band AS by excitation light not absorbed at 4,48
E light is generated, and the L band signal light Lb is amplified by this and a part of the C band ASE light from the EDFs 44 and 48. The L-band signal light Lb optically amplified by the EDF 46 is:
The light is slightly amplified by the EDF 44 and enters the port B of the optical circulator 40. Optical circulator 40 is port B
Is output from the port C, the L-band signal light Lb amplified by the EDF 48 is eventually input to the gain equalizer 68 via the optical circulator 40.

Thus, the gain equalizer 68 has E
The C-band signal light Cb optically amplified by the DF 48 and the EDF
The L-band signal light Lb optically amplified at 46 is input. The gain equalizer 68 adjusts the gain of the input signal lights Cb and Lb, and outputs the signal light to the output port 34.

The signal lights Cb and Lb thus optically amplified by the optical amplifier 30 are supplied from the output port 34 to the optical fiber 14.
And propagates through the optical fiber 14 and enters the reception port Rx of the terminal station 10.

In this embodiment, since the EDF 46 is used bidirectionally for amplifying the signal lights La and Lb, the number or length of the optical amplifying medium can be reduced. As a result, a wideband optical amplifier can be realized with a small number of elements.

Although the embodiment applied to the optical transmission system using separate optical fibers for upstream and downstream has been described, this embodiment is a bidirectional transmission system for transmitting signal light bidirectionally over one optical fiber line. It can also be applied to optical transmission systems. An optical circulator may be arranged between the input port 32 and the output port 34, and an optical circulator may be arranged between the input port 36 and the output port 38. FIG. 2 shows a schematic block diagram of the modified embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals.

The transmission / reception port of the terminal station 70 is an optical fiber 72.
To port B of an optical circulator 74 having three ports A, B, and C. The port A of the optical circulator 74 is connected to the output port 34 of the optical amplifier 30,
The port C of the optical circulator 74 is connected to the input port 32 of the optical amplifier 30.

The transmission / reception port of the terminal station 76 is an optical fiber 78.
To the port B of the optical circulator 80 having three ports A, B, and C. The port A of the optical circulator 80 is connected to the output port 38 of the optical amplifier 30,
The port C of the optical circulator 80 is connected to the input port 36 of the optical amplifier 30.

It goes without saying that a bidirectional optical amplifier comprising the optical amplifier 30 and the optical circulators 74 and 80 may be further disposed on the optical fibers 72 and 78.

The operation and signal flow of the embodiment shown in FIG. 2 will be described. C-band signal light Ca output from the terminal station 70
And the L-band signal light La enters the input port 32 of the optical amplifier 30 via the optical fiber 72 and the ports B and C of the optical circulator 74. The optical amplifier 30 amplifies the signal lights Ca and La input to the input port 32 as described above, and outputs the amplified signal light from the output port 38. Optical amplifier 30
The signal light Ca, which is amplified at and output from the output port 38,
La is input to the terminal station 76 via the ports A and B of the optical circulator 80 and the optical fiber 78.

The C-band signal light Cb and the L-band signal light Lb output from the terminal station 76 are input to the input port 36 of the optical amplifier 30 via the optical fiber 78 and the ports B and C of the optical circulator 80. . Optical amplifier 30
Amplifies the signal lights Cb and Lb input to the input port 36 as described above, and outputs the amplified signal light from the output port 34. The signal lights Cb and Lb amplified by the optical amplifier 30 and output from the output port 34 are output from the ports A and B of the optical circulator 74.
The signal is input to the terminal station 70 via the optical fiber 72.

In the above embodiment, the gain equalizers 66 and 68 are arranged on the output side of the optical couplers 62 and 64. That is,
After the amplified C-band and L-band signal lights are multiplexed, the gains are collectively equalized. However, the amplified C
After individually equalizing the gains of the band and L-band signal lights, they may be combined.

[0039]

As can be easily understood from the above description, according to the present embodiment, a bidirectional optical amplifier having a wide band can be realized with a small number of elements. By reducing the number of elements,
Reliability is improved. The number of excitation light sources can be reduced, which also contributes to improvement in reliability.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a first embodiment of the present invention.

FIG. 2 is a schematic configuration block diagram of a second embodiment of the present invention.

[Explanation of symbols]

10: terminal station 12, 14: optical fiber 16: terminal station 18, 20: optical fiber 30: bidirectional optical amplifier 32: input port 34: output port 36: input port 38: output port 40, 42: optical circulator 44, 46, 48: Erbium-doped optical fiber (ED
F) 50: laser diode 52: WDM optical coupler 54: laser diode 56: WDM optical coupler 58, 60: band splitting filter 62, 64: optical coupler 66, 68: gain equalizer 70: terminal station 72: optical fiber 74 : Optical circulator 76: Terminal 78: Optical fiber 80: Optical circulator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04J 14/02 (72) Inventor Morita Itsurou 2-1-1-15 Ohara, Kamifukuoka-shi, Saitama Inside the laboratory (72) Inventor Noboru Egawa 2-1-1-15 Ohara, Kamifukuoka City, Saitama Prefecture Inside Kadeidi Co., Ltd. F-term in the laboratory (reference) 5F072 AB09 AK06 JJ20 PP07 RR01 YY17 5K002 AA06 BA02 BA05 CA10 CA13 DA02 DA04

Claims (6)

[Claims] 1. A first signal light (L) of a first band (L).
a) First input light composed of the second signal light (Ca) of the second band (C), and third signal light (Lb) and the second band of the first band (L) An optical amplifying device for amplifying the second input light composed of the fourth signal light (Cb) of (C), wherein the first optical amplification medium is capable of amplifying the light of the first band (L). (46) and second and third optical amplifying media (44, 48) arranged on both sides of the first optical amplifying medium (46) and capable of amplifying the light of the second band (C). An excitation light source for generating excitation light for exciting the first, second, and third optical amplification media; and first, second, and third ports, which are input to the first port (A). The first input light is supplied from the second port (B) to the second optical amplification medium (44), and is supplied from the second optical amplification medium (44). The second port (B)
To output light from the third port (C)
Optical circulator (40), and first, second, and third ports, and the second input light input to the first port (A) is transmitted from the second port (B) to the third port. To the second port (B) from the third optical amplification medium (48).
Output from the third port (C).
The optical circulator (42), and the first optical amplifying medium (46) and the second optical amplifying medium (44) are disposed between the optical circulator (42) and the second optical amplifying medium (4).
A first wavelength separator (58) for separating the two signal lights (Ca) amplified in 4), the third optical amplifying medium (48), and the first optical amplifying medium (46). And the third optical amplifying medium (4
A second wavelength separator (60) for separating the four signal lights (Cb) amplified in 8), and the first light to the light output from the third port of the second optical circulator (42). A first multiplexer (62) that multiplexes the light separated by the wavelength separator (58), and a second multiplexer that combines the light output from the third port of the first optical circulator (40). An optical amplifying device comprising: a second multiplexer (64) for multiplexing the light separated by the wavelength separator (60). 2. A first gain equalizer (66) for equalizing a gain of output light of the first multiplexer (62), and an output of the second multiplexer (64). The optical amplifying device according to claim 1, further comprising a second gain equalizer (68) for equalizing light gain. And a second optical circulator (4).
2) a first gain equalizer (66) for equalizing the gain of the output light from the third port, and the first wavelength separator (58)
Gain equalizer (6) for equalizing the gain of the light separated by
6), a third gain equalizer (68) for equalizing the gain of the output light from the third port of the first optical circulator (40), and the second wavelength separator (60). The optical amplifying device according to claim 1, further comprising a fourth gain equalizer (68) for equalizing a gain of the separated light. 4. The pump light source includes a first pump light output device (50), a second pump light output device (54), and a second port (B) of the first optical circulator (40). And the second optical amplification medium (44),
A first WDM optical coupler (52) for supplying pump light output from the pump light output device (50) to the second optical amplification medium (44), and the second optical circulator (4).
2) of the second port (B) and the third optical amplification medium (4
8), and the second pumping light output device (5
The pump light output from the fourth optical amplifying medium (4)
The optical amplifying device according to claim 1, further comprising a second WDM optical coupler (56) for supplying the optical coupler to the optical amplifier (8). 5. The pumping light source includes a pumping light output device (50, 54) that outputs the pumping light, a second port (B) of the first optical circulator (40), and the second optical amplifier. A part of the excitation light output from the excitation light output device (50, 54) is disposed between the mediums (44),
Between the first WDM optical coupler (52) supplying the optical amplification medium (44) of the second optical circulator (42) and the second port (B) of the second optical circulator (42) and the third optical amplification medium (48). And the rest of the pump light output from the pump light output device (50, 54) is transferred to the third optical amplifying medium (48).
The optical amplifying device according to claim 1, further comprising a second WDM optical coupler (56) for supplying the optical coupler to the second WDM optical coupler. 6. The optical amplifier according to claim 1, wherein the first band is an L band and the second band is a C band.